There are various kinds of base materials for the plastic lens substrate. The material can be selected depending on the application or use environment of the user. For example, a great number of plastic lenses using a high refractive index substrate having a refractive index of 1.67 or more have been developed. Such a plastic lens using a high refractive index substrate is particularly useful, for example, for patients who require a lens having a high power of ±6.00 or more since the lens can be thinned, and thus it is in high demand.
In addition, a plastic lens substrate formed of a polycarbonate material (refractive index: 1.59) or a polyurethane material (refractive index: 1.53) is known as a highly impact-resistant lens since it exhibits excellent toughness.
On the other hand, plastic lenses generally have a low surface hardness, which is a drawback in abrasion resistance. Hence, it has hitherto been carried out to provide a hard coat layer on the plastic lens surface in order to compensate for this weakness.
However, interference fringes are caused in some cases in the case of forming a film such as a hard coat layer on the lens surface. This is because light is reflected at the interface between the lens substrate and the film due to the difference in refractive index between the lens substrate and the film and this light causes interference. The interference is likely to remarkably occur particularly in the case of a plastic lens having a high refractive index since the difference in refractive index between the lens substrate and the hard coat layer is greater in that case.
In Patent Literature 1, an optical product, such as a lens for spectacle, includes an organic or mineral glass substrate and at least one transparent high molecular substance layer. The interference fringe phenomenon occurring at the interface between the substrate and the high molecular substance layer is significantly suppressed with regard to the difference in refractive index between the substrate and the high molecular substance layer by an undercoat layer or abrasion-resistant coating layer. In the literature, an optical product is disclosed which includes at least one intermediate layer in direct contact with one main surface of the substrate and a high molecular substance layer and in which the intermediate layer has particles of at least one colloidal mineral oxide and optionally a binder. The intermediate layer has an initial void. The initial void of the intermediate layer is filled with a substance from the polymeric material layer or a substance of the substrate in a case in which the substrate is organic glass. The initial void may be partially filled with the binder in a case in which the binder is present. The intermediate layer becomes a quarter-wave plate at the wavelength in a range of from 400 to 700 nm and preferably from 450 to 650 nm, respectively, after the initial void is filled.